Effect of Rainfall on Stream Fish Communities

Effect of Rainfall on Stream Fish Communities

Sean Kinard
Department of Biological Sciences
Virginia Institute of Marine Sciences

Streams are dependent on water availability, making them vulnerable to expected changes in the hydrologic cycle and growing anthropogenic demands upon freshwater sources. Here, we discuss how aridity imposes harsh physical conditions which decrease diversity and favor salinity-tolerant and live-bearing species. To enhance our understanding of the effects of precipitation on stream communities we applied a space for time approach along a natural rainfall gradient (50-130 cm/yr) spanning 300 km in South Central Texas.  Algal assays and stable isotope analyses reveal a shift towards in-stream resources as the climate becomes drier, in addition to shortening food chain length and narrowing isotopic niche space. Lastly, arid systems exhibited the least community resistance to hurricane disturbance and had slower recovery-times which can be attributed to a greater flood magnitude and shorter flood duration. We apply these results with tenets of the flood-pulse and river-continuum concepts to create a new precipitation-oriented model which can be applied across systems.  It is also our goal to create a predictive framework to guide hydrological and riparian management strategies to mitigate the undesired consequences of climate change on stream communities.

Streams are dependent on water availability, making them vulnerable to expected changes in the hydrologic cycle and growing anthropogenic demands upon freshwater sources. Here, we discuss how aridity imposes harsh physical conditions which decrease diversity and favor salinity-tolerant and live-bearing species. To enhance our understanding of the effects of precipitation on stream communities we applied a space for time approach along a natural rainfall gradient (50-130 cm/yr) spanning 300 km in South Central Texas.  Algal assays and stable isotope analyses reveal a shift towards in-stream resources as the climate becomes drier, in addition to shortening food chain length and narrowing isotopic niche space. Lastly, arid systems exhibited the least community resistance to hurricane disturbance and had slower recovery-times which can be attributed to a greater flood magnitude and shorter flood duration. We apply these results with tenets of the flood-pulse and river-continuum concepts to create a new precipitation-oriented model which can be applied across systems.  It is also our goal to create a predictive framework to guide hydrological and riparian management strategies to mitigate the undesired consequences of climate change on stream communities.

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